Electronic devices include traditional computing devices such as desktop computers, notebook computers, smart phones, wearable devices like a smart watch, server computers, and the like. However, electronic devices also include other types of computing devices such as personal voice assistants, thermostats, automotive electronics, robotics, devices embedded in other machines like refrigerators and industrial tools, Internet-of-Things (IoTs) devices, and so forth. These various electronic devices provide information, entertainment, social interaction, security, safety, productivity, transportation, and other services to human users. Thus, electronic devices play crucial roles in many aspects of modern society.
Many of the services provided by electronic devices in today's interconnected world depend at least partly on electronic communications. Electronic communications can include those between and among widely distributed electronic devices using wireless or wired signals over one or more networks, such as the Internet or a cellular network. Electronic communications can also include those between different printed circuit boards, modules, chips, and cores or other circuitry of an integrated circuit within a single electronic device. Regardless, electronic communications are usually accomplished by generating or propagating signals. Typically, such electronic communications are performed more quickly or more reliably by controlling the relative timing of a signal in relation to one or more other signals.
A timing of a signal in relation to another signal is referred to as a phase difference between the two signals, or relative phases between the two signals. To use a signal to facilitate electronic communications, the phase of the signal is adjusted in many circumstances. The phase of a signal can be adjusted by, for example, delaying the signal. A delay locked loop (DLL) is a digital circuit that can delay a signal to introduce a phase shift or phase delay into the signal to produce a delayed signal. The delayed signal can be used to facilitate a timing alignment with another signal, to generate a radio frequency (RF) transmission signal, and in other usage scenarios.
In one example usage scenario, a delay locked loop can be used to shift a phase of a signal, such as a clock signal. The phase-shifted clock signal can enhance a clock rise timing with respect to a valid output timing of a data signal, with the data signal having data that is to be obtained via a sampling of the data signal responsive to the clock rise timing. The delay locked loop shifts the clock signal for the data sampling such that a rising edge of the clock signal is likely to occur near the middle of a time period during which a data value of the data signal is expected to be valid. This increases the likelihood of successfully acquiring the data signal while the data value is valid.
In another example usage scenario, a delay locked loop can shift a phase of a clock signal by some number of degrees, such as 45 degrees, to facilitate transmission of signals at radio frequencies. For instance, a harmonic rejection mixer (HRM) is employed in some radio frequency (RF) transceivers, such as by an RF transmitter thereof, to reduce the occurrence of spurious harmonic frequencies that can lower a quality of a transmission signal. An HRM typically uses at least four different phases of a clock signal (e.g., 0°, 45°, 90°, and 135°-shifted versions of the clock signal) to filter out, or at least reduce, the undesired harmonic frequencies. A delay locked loop can therefore be used to generate any of the four different phases of the clock signal for used by an HRM.
Thus, delay locked loops are employed in multiple different usage scenarios to support electronic communications with electronic devices. Consequently, electrical engineers and other designers of electronic devices strive to improve the functionality and usability of delay locked loops to facilitate electronic communications with electronic devices.